1. Field of the Invention
The present invention relates to a pipe coupling which can be manufactured and shipped in a substantially flat configuration and which provides a flexible coupling joint achieved by employing a flexible sleeve member, flexible teeth or a combination thereof to provide a flexible yet strong connection for corrugated drain pipe that is twisted and bent during ground laying operations. More particularly, the invention pertains to a flexible pipe coupling having a substantially rectangular shaped flexible sleeve member having disposed thereon at least two rows of teeth along the length of the sleeve for engaging at least one corrugated groove of each section of abutting pipe to accommodate a wide variety of corrugated pipe configurations.
2. Description of the Prior Art
A variety of couplings exist for joining various types of corrugated pipe. One form of circularly and spirally corrugated pipe is the rigid metal conduit type pipes which employ a variety of virtually rigid couplings for joining sections of pipe. Representative of this type of coupling are U.S. Pat. Nos. 3,239,254 (FIG. 5); 3,501,179 (FIG. 7); 3,708,187 and 4,061,368.
Corrugated metal pipes and pipe couplings for metal pipes and markedly different from corrugated plastic drain pipes and couplings therefor. In metal conduit pipes the trenching and pipe laying operations are not carried out in a single operation in that metal pipe couplings do not simultaneously require the inconsistent requirements of flexibility and strength required of couplings employed for corrugated plastic drain pipe. Couplings for plastic corrugated drain pipe must furthermore not have flanges which significantly protrude from the outside circumference of the coupling which can become lodged in the trencher, resulting in shearing of the plastic pipe, failure of the joint and considerable interruption in trenching operations.
Corrugated plastic drain pipe in contrast to corrugated metal conduit pipe is employed for draining swamps and fields and is installed by employing a trencher which simultaneously digs a trench, lays the drain pipe line and with some trenchers also covers the installed drain pipe. During the installation of the plastic corrugated drain pipe the pipe is required to make a number of bends and turns while being twisted and under tension as it moves from the position above ground on the trencher down through a guide down to the trencher shoe and into the trench. Furthermore, as there is no set standard the manufacturers of corrugated plastic drain pipe utilize their own distinctive lip and groove configuration.
The lack of uniformity between the size, shape, height and width of the groove in corrugated plastic drain pipe in conjunction with the procedure for installing such pipes has presented considerable problems in providing a coupling for joining sections of drain pipe. One such prior art coupling for joining sections of corrugated plastic drain pipe is described in U.S. Pat. No. 3,899,198. Another prior art coupling of widespread use in the field consists of a split plastic sleeve having an appearance similar to the corrugated drain pipe. In use this coupling is spread open and the corresponding sections of pipe inserted therein to mate with corresponding grooves disposed on the drain pipe. These prior art couplings are generally the same diameter or of a slightly larger diameter so that they can be tied in place with either a bailing wire or twine.
Hand tied couplings not only required considerable time in opening the couplings but also required a high degree of care. When twine was employed, the hand tied knot had to be reasonably tight in the groove of the sleeve to secure the lip and groove of the underlying drain pipe to prevent slippage. On the other hand, use of wire to fasten the coupling assured a reasonably tightly secured coupling but resulted in coupling failures caused by the tie wire becoming caught in the guide or shoe of the trencher. In addition, hand tied wire stressed the tying wire so that the stretching involved with the installation and covering of the pipe caused the wire to break and the coupling to fail.
It is critically important in drain pipe joining operations that the sleeve or coupling utilized for joining the pipe sections does not allow the sections to become disconnected during trenching, pipe laying and covering operations. Coupling failure at the least interrupts valuable trenching time and requires stopping the trencher, digging up the pipe and then recoupling the sections. Alternatively, failure to immediately ascertain coupling failure results in improper field drainage requiring ascertaining the point of failure, removing crops or structure and then digging up the line to repair the coupling.
The prior art couplings for joining corrugated plastic drain pipe not only exhibit the disadvantage of requiring considerable hand labor and time to join sections of pipe but also result in increased expense due to the inefficiency in packing, shipment and application of prior art circular couplings. The problems resulting from the conditions required for plastic drain pipe couplings and the difficulties resulting when such couplings do not maintain their integrity in trenching operations reveal many of the problems involved with prior art couplings.